There is nothing wrong with fiat currencies, which is what all currencies really are, even the value of gold is a convention, as you can't eat gold.

Bitcoin may even said to be based on the "labor value" of the electricity needed to produce it, since if it moves under that bar, mining would stop. The real value of bitcoin is that it is the first globally scaleable, easy to use, socially sovereign currency.

Unlike the local currencies which do not scale (a study showed their average number of users to be 80-120 per currency); on the other hand, Bitcoin is designed to be scarce and thus a hoarding currency. It is perhaps why it is successful, but also makes it a transition currency. Freicoin could be it, but I'm afraid they messed up the introduction phase with their 80% initial tax.

(My response to Michel)
My point is that in order to work as a sustainable currency it must be based upon a claim over future value, not past value.

I see two principal sources of value for acceptable currency: land rentals and energy.

I see the capacity to provide goods and services as being the basis not of currency, but of the framework of trust for credit clearing. Neither currency, nor deposits are required for 'people-based' credit creation, clearing and settlement.

Although a unit of account IS necessary to value exchange transactions, this is not the same thing as the 'asset-based' (Peer to Asset) currencies and people-based' (P2P) credit obligations which may be exchanged by reference to it.

'Hoarding currency' is not currency: it's capital, and it represents only potential currency which requires acceptance from a counter-party in exchange in order to be valuable.

Since Bitcoin does not represent a claim over future value, I don't see it as ever going beyond the existing constituency for whom its value lies in Bitcoin maintaining anonymity and security.

"The future is already here -- it's just not very evenly distributed"
William Gibson